In the past, various techniques have been proposed to reduce the power consumption of an electronic device. For example, there is a technique in which data in a main memory or a processor is saved in a nonvolatile storage device when there is no input from the outside within a predetermined period of time, and power supply to the main memory or the processor is stopped so as to let an electronic device go into a sleep mode (low power mode). In the technique, when an input (for example, a wakeup event signal of exiting the sleep condition such as a touch operation of a panel or a mouse) is received from the outside in the sleep mode, the data saved in the nonvolatile storage device is returned into the main memory or the processor, and the electronic device is returned to a state before the electronic device goes into the sleep conditions as to restart a process.
In the traditional technique, when exiting the sleep mode, the electronic device goes into the same state as the state before the electronic device goes into the sleep mode, and thus an equivalent of power before the electronic device goes into the sleep mode is necessary. However, depending on states of a power source, the equivalent of the power before the electronic device goes into the sleep mode may not be obtained.